Catalysts for use in organic syntheses have long been studied, and a variety of catalysts have been prepared and used for various purposes. Development of separation techniques of optically active substances has stimulated investigations on asymmetric syntheses and the results of such investigations have been published. Simultaneously, extensive studies on asymmetric catalysts for use in asymmetric syntheses such as an asymmetric isomerization reaction and an asymmetric hydrogenation reaction have been made in recent years.
Many transition metal complexes have heretofore been used as catalysts for preparation of organic compounds. In particular, noble metal complexes are stable and are easy to handle although those are expensive. Thus, extensive investigations are being made on organic syntheses utilizing such noble metal complexes as catalysts. In recent years, organic synthesis reactions which are impossible to perform by other techniques have been reported.
In general, rhodium, palladium and nickel catalysts with tert-phosphine as an optically active ligand provided thereto give good results. Japanese Patent Application (OPI) No. 61937/80, for example, discloses a rhodium/phosphine catalyst as an asymmetric hydrogenation catalyst, in which chiral phosphine is coordinated to rhodium. The term "OPI" as used herein means a "published unexamined Japanese patent application".
Japanese Patent Application (OPI) No. 4748/83 discloses a method of preparing enamines or imines by isomerization of allylamine derivatives using as an asymmetric isomerization catalyst a rhodium complex represented by the formula (II): EQU [Rh(olefin)L].sup.+ X.sup.-
wherein the olefin represents ethylene, 1,3-butadiene, norbornadiene or cycloocta-1,5-diene; X represents ClO.sub.4, BF.sub.4 or PF.sub.6 ; and L represents two triarylphosphines or a trivalent phosphine compound represented by the formula (III): ##STR1## wherein Y is --(CH.sub.2).sub.3 --, --(CH.sub.2).sub.4 --, --(CH.sub.2).sub.5 --, R1 ? ##STR2## For example, neryldiethylamine is subjected to isomerization and the enamine thus prepared is hydrolyzed to obtain optically active citronellal.
Japanese Patent Application (OPI) No. 20294/84 describes a method of preparing a rhodium complex represented by the structural formula: [Rh(olefin)BINAP].sup.+ Y.sup.-, and also a method of preparing (R)-3-methoxy-4-acetoxyphenylanine in high yield by asymmetic hydrogenation of 3-methoxy-4-acetoxyacetamidecinnamic acid using the rhodium complex catalysts.
These catalysts, however, have various disadvantages. One of the disadvantages is that their production costs are high since they are prepared using expensive metals and, furthermore, they are difficult to prepare and require a series of steps in preparation thereof. This results in increasing the price of the desired compound. Another disadvantage is that although their catalytic activity is high, such a high activity cannot be maintained for long periods of time, or conversely, although their catalytic life or durability is long, activity is relatively low. Thus, they are not suitable for use in industrial applications.
Under such circumstances, it has been desired to develop catalysts which are inexpensive, have a high activity and can maintain such a high activity for long periods of time.